Discoveries under the walls suggest that people lived and held rituals here well before most of these mounds were built. During the first century A. D., a few ceremonial houses were put up; their fire-basins and doorways had a variety of orientations. Some of these were probably mounded over by the time the second phase began, at the start of the second century.

Three central buildings were erected, creating a new ritual focus. At least seven other buildings were built, pointing towards this focus. And the low wall was added to enclose things, strengthening the formality of the site, and its sense of common purpose. It resembles the shape of an individual building; and its two gates define an axis. This centralization and enclosure of the whole site may reflect an increasing organization and social ranking among the people. By the early third century, mounding was complete.

Plan of Mound City showing the orientation of the sub-mound structures, and the dominance of the central features.